(1.) Technical Field
The subject invention is directed toward a test mold for use in reactive injection or conventional type molding operations and, more specifically, to test molds adapted to produce molded parts having simulated voids therein for evaluating the effect of these voids on the surface appearance of the coverstock.
(2) Description Of The Prior Art
Reaction injection molding processes are well known in the prior art and are extensively employed, for example, to bond a polyvinyl chloride coverstock to a foam base portion, which, in turn, is usually supported by a support structure. Reaction injection molding processes of this type are commonly used in the manufacture of instrument panels.
One parameter which is important to the manufactures of such products is the appearance of the coverstock when bonded to the foam. During the molding process, voids in the foam can form which produce irregularities on the coverstock or otherwise effect the surface appearance of the coverstock. As such, it is important to study this phenomena.
One method of studying the effects on the coverstock caused by voids in the foam employed in the past was to identify defective parts during the course of manufacturing the product using regular quality control procedures and then environmentally cycling the parts and analyzing the effects of these tests on the parts. Unfortunately, it is difficult to identify defective products having voids in the foam because they are not visible upon sight inspection. This method was therefore unpredictable. Furthermore, reliance upon production run instrument panels or other products as a source of test models was expensive.
These problems were addressed by the test mold disclosed in U.S. Pat. No. 4,936,762 issued to Gaudreau et al on Jun. 26, 1990 and assigned to the assignee of the subject invention. The test mold disclosed in this patent has various sized, spaced apart, aligned openings formed in each of the front and rear walls of the mold, but with the centers thereof at different elevations in their respective front and rear walls. Removable rods inserted through the aligned mold wall openings produce longitudinal openings through the part which is molded around the rods permitting the effect thereof on the surface of the molded part to be evaluated. In this way, a foam model having voids therein could be manufactured under controlled conditions and scientifically tested without the cost associated with special quality control procedures and scrapping production part.
Although eliminating some of the problems of the prior art set forth above, the test mold of the '762 patent was deficient in that the voids created by the rods did not accurately model the voids typically found in production parts. More specifically, the geometry of voids typically found in production parts most closely approximate an ellipse having a major and minor axis. The rods of the Gaudreau et al test mold are cylindrical in shape and have a circular cross section. Furthermore, in order to vary the geometry of the voids created in the foam, both the rods and the openings in the side walls must be changed. As such, the realities of this situation dictate that a different test mold be made for each void geometry to be investigated.
The subject invention overcomes the problems associated in the prior art and addresses the deficiencies of the '762 patent in an efficient, cost effective flexible coverstock semi rigid foam void test mold and method of making a foam void model.